Ore concentrator



Jan. 17, 1933.

H. c. MITCHELL 1,894,779

ORE CONGENTRATOR Filed Oct. 8, 1931 2 Sheets-Sheet l 0o 00000 0000000000 0000000000 00000000 00 000000000 0000000000 0000 00 0000 0000000000 0000000000 oooooooooo 0000 000000 0000000000 0000000000 0000000000 0000 000000 420000000 00 INVENTOR, 7' 6.

BY M ATTORNEY 2 Sheets-Sheet 2 NTCR Jan. 17, 1933. c. MITCHELL ORE CONCENTRATOR Filed Oct. 8, 1951 R I am Patented Jan. 17, 1933 UNITED STATES PATENT OFFICE HENRY C. MITCHELL, OF NATURITA, COLORADO, ASSIGNOB, OF ONE-HALF TO PAUL STARK SEELEY ORE GONC'ENTRATOR Application filed October 8, 1931.

My invention relates to that class of devices which are designed to separate fine an light free gold from placer gravel.

My invention has for its object to con-4 struct a device which will be more eflcient in its operation by an increased recovery of the fines than is possible with the present forms of apparatus employed for this purpose.

My invention has for a further object to provide a device which will operate equally well with mill slimes.

A further object is to provide a device which will be most economical and eflcient h for use on dredges employed for the recovery of gold in rivers and along their courses.

My means of accomplishing the foregoing objects may be more readily understood by having reference to the accompanying drawings, in whichv I Fig. 1 is a plan view of my improvement;

Fig. 2 is a section taken on the line 2-2 of Fig. 1 in the direction indicated by the arrows;

Fig. 3 is a section taken on the line 33 of Fig. 1, in the direction indicated by the arrows; and

Fi 4 is an enlarged fragmentary view of a r' e. Similar reference numerals refer to similar parts throughout the entire description.

As shown in the drawings, my device consists of a rifle box 1, mounted above the rifle box is a grizzly 2 which preferably consists of a plate of iron provided with a plurality of perforations 3. These perforations should be preferably to 5 of an inch in diame ter, depending upon the fineness of the gold and the character of the gravel or the nature of the mill slimes which are to be handled. As shown, the grizzly 2 is supported upon shoulders 4 and 5, which should be approximately 1 inch above the rifle board 6 which forms the bottom of the rifle box 1. The rifle box 6 is provided with a plurality of rifles 7, each of which has a continuous discharge. The first rifle starts 2 inches from the lead and on either side depending on whether it is designed to discharge to the right or left for a single rifle board may be made to discharge either to the right or to Serial No. 567,566.

the left or the device may be made up with duplicate rifle boxes, one of which discharges to the right and the other to the left. It will be apparent to persons skilled in the art that the rifle boards 6 may be of any width desired limitedonly by the amount of water available for the sluice lead. The rifles 7 angle across the rifle board 6 at approximately an angle of 45. They are undercut, as clearly shown in Fig. 4.- of the drawings, and are preferably constructed with a depth of at the initial point expanding to 1%" at its discharge point 8. I desire it to be understood that I do not wish to be limited to the exact shape of the rifles or the angle of their inclination as any form may be used which will handle the material as needed. In practice I have found it desirable to provide for an inclination of the rifle board 6 of substantially 1 inch to 1 foot. The rifle board may be constructed of any suitable material such as wood, metal, rubber products or any combination thereof which may be desirable. At the discharge end 8, of W each rifle 7, I provide a round opening 9, which is directly in line with the bottom of the rifle 7. The rifles constantly discharge the gold concentrates through these openings. Over these openings 9, I mount hoods 10, which are shaped as clearly seen in the drawings witha reverse portion 11 which operates to reverse the direction of the flow and to throw the stream back towards the point of its discharge. The hood 10 terminates at a point 11 which is located close to the bottom 12 of the launder 13 and spreads the flow evenly in a lamina across the entire width of the launder 13. In practice I have found it desirable to make these launders substantially sixfeet long, 15 inches wide and two inches deep.

I have found in practice that a greatly increased recovery can be had by covering the floor 12 of the launders 13 with a fabric 14 which has a nap or weave into which the fine gold will settle such as carpet, burlap or similar material. The fabric is detachably secured in place by bolts 15 which are provided with wing nuts 16 for convenient removal.

The rifle box should be maintained exactly level on its cross dimension but is given the longitudinal inclination heretofore mentioned. Obviously this may be varied to suit the character of the work such as the quantity of water and the nature of the material handled.

The operation of the device is as follows:

The material is discharged onto the grizzly 2, the water flowing underneath will draw the finer part thereof, which contains the valucs,throughtheperforations by hydraulic suction, while the coarser material, due to the inclination, will pass to the tailing dump. It is well known that the fine gold will remain in suspension in the presence of the gravel where the grade is greater than 1 inch to the foot more or less depending on the nature of the gangue. The fine values drop into the riffies, where the light finer precious metal values are panned out by the water stream and the heavier fines are worked down the rifles and discharged into the hood 10. Since the finer gold values are still in suspension it is necessary, in order to throw it down, to spread the stream and material carried by it in a lamina across the fabric 14. The nap or weave will catch and hold the fine gold. It is well known that a flowing stream of water has a rolling movement due to the fact that the friction against the stream bed causes the water adjacent thereto to move slower than the top. I avail myself of this law and make use of this rolling motion to throw down the fine gold into the nap or weave of the fabric from which it may subsequently be recovered by washing or amalgamation.

Although I have described and illustrated certain details of construction, it is to be understood I have done so only for the purpose of disclosing a preferred embodiment of my invention which I have found in actual practice to be highly efiicicnt; but this disclosure is not to be deemed a limitation except as such limitations appear in the hereinafter contained claims.

Having described my invention what I regard as new and desire to secure by Letters Patent is:

1. The combination with a grizzly, of a rifle box below said grizzly, there being a plurality of lateral discharge outlets from said rifle at the ends of the rifles in said rifle box, a launder adjacent each discharge, a hood for each outlet which directs the flow backwards towards said outlet and spreads it in a lamina which extends the width of said launder and a lining of fibrous material on the bottom of said launders.

2. The combination with a grizzly, of a rifle box below said grizzly, a plurality of undercut rifles in said box which extend in an angular direction across said box, said cuts expanding from 4 in depth at the upper end to 1 at the lower or discharge end, there being a plurality of outlets in said rifle box at the discharge end of said rifles, a launder adjacent each discharge hood for each outlet which directs the flow backwards towards said outlet and spreads it in a lamina which extends the width of said launder, the bottom of said launder being lined with fibrous material.

3. The combination with a grizzly of a rifle box, there being side openings in said box, rifles on said box, a discharge hood at the end of said rifles, launders into which said hood directs the said discharge, a lining ofv rough surfaced material in said launder.

4. The combination with a grizzly of a rifle box, below said grizzly, there being side openings in said box, a plurality of rifles in said box, said rifles being undercut, angular and expanding, a launder below each of said side openings, a discharge hood at each side opening which directs the flow back upon itself and forms a lamina in said launder, and a lining of rough surfaced material on the bottom of said launder.

5. The combination with a rifle box having side openings therein, of a plurality of rifles in said box, said rifles being undercut and angular and expanding from in depth to 1 in depth at the discharge, a launder at each side opening, a discharge hood at each side opening which directs the flow back upon itself which forms a lamina the width of the launder and a lining of rough surfaced material on the bottom of said launder.

6. The combination with a grizzly, of a rifle box below said grizzly, a plurality of rifles in said box, said rifles being undercut, angular and expanding, launders at each side opening, said launders having the bottoms lined with rough surfaced material and a hood to spread the flow in a lamina over said rough surfaced material.

7. The combination with a grizzly, of a rifle box below said grizzly, a plurality of rifles in said box, there being an opening in said box at the lower end of each rifle, a discharge hood for each of said openings which directs the flow back' upon itself, launders below said openings, said hood forming a lamina, the width of said launders and a lining of rough surfaced material at the bottom of said launders.

8. The combination with a grizzly, of a rifle box below said grizzly, there being side openings in said box, a plurality of undercut expanding rifles in said box, a launder at each of said openings, a discharge hood for each of said openings which directs the flow back upon itself and forms a lamina which extends the width of said launder and a lining of rough surfaced material for the bottom of said launders.

9. The combination with a rifle box having a plurality of rifles in said box, said rifles being undercut, angular and expanding and leading to side openings of a launder at each side opening, said launders having the bottoms lined with rough surfaced material and means to spread the discharge from said rifles in lamina over said rough surfaced material.

10. The combination with a rifle box, of a plurality of rifles in said box, there being an opening in said box at the lower end of each rifle, a discharge hood for each of said openings which directs the flow back upon itself, launders below said openings, said hood forming a lamina, the width of said launders and a lining of rough surfaced material at the bottom of said launders.

11. The combination with a rifle box,

there being side openings in said box, a

plurality of undercut, expanding rifles in said box of a launder at each of said openings, a discharge hood for each of said openings, which directs the flow back upon itself and forms a lamina which extends the width of said launder and a lining of rough surfaced material for the bottom of said launders.

12. The combination with a grizzly, with a rifle box, below said grizzly, there being side openings in said box, a plurality of rifles in said box, said rifles being undercut and expanding, of a launder below each of said side openings, a discharge hood at each side opening which directs the flow back upon itself and forms a lamina in said launder, a lining of rough surfaced material on the bottom of said launder.

13. The combination with a grizzly, of a rifle box below said grizzly, there being side openings in said box, a pluralityof undercut rifles in said box, of a launder at each of said openings, a discharge hood for each of said openings which directs the flow back upon itself and forms a lamina which extends the width of said launder and a lining of rough surfaced material for the bottom of said launders.

14. The combination with a grizzly with a rifle box, below said grizzly, there being side openings in said box, a plurality of undercut rifles in said box, said rifles being undercut, angular and expanding, of a launder below each of said side openings, a discharge hood at each side opening which directs the flow back upon itself and forms a lamina in said launder, a lining of rough surfaced material on the bottom of said launder, and means to detachably secure said material to the bottom of said launders.

HENRY C. MITCHELL. 

